Public and private efforts to sequence the mouse genome bore fruit in 2002 as researchers confirmed and expanded the notion that almost any gene in humans is also present in mice.

In April 2001, Celera Genomics in Rockville, Maryland, announced
the completion of a draft mouse genome sequence, which was made
available to subscribers of the company's database. One year later,
Celera scientists reported new information about similarities between
man and mouse. They found just fourteen genes on mouse chromosome
16 that have no obvious counterparts in humans. All the othersmore
than 700 mouse genesare present in humans. Furthermore, the
human genes reside together and in virtually the same order as in
the mouse genome.

Humans and mice, it appears, have about 200 genomic blocks that
contain the same genes but are arranged on different chromosomes.
Short stretches of genetic code within these blocks have been conserved
during mammalian evolution, the Celera team reported in Science.

In December 2002, the international Mouse Genome Sequencing Consortium
completed a draft of the mouse genome and compared it to the human
genome. Both species have about 30,000 genes, the researchers reported
in Nature. They identified in mice two thousand 'non-gene'
regions that are also present in humans. These regionssometimes
referred to as 'junk DNA'may perform important functions,
such as regulating genes.

The researchers discovered about 9,000 previously unknown mouse
genes and 1,200 previously unknown human genes. With about 2.5 billion
letters of DNA, the mouse genome is 14 percent smaller than its
human counterpart. Like Celera, the Consortium sequenced the mouse
using the whole-genome shotgun method.